As the number of Internet users and Internet-based mission-critical applications increase daily at an unprecedented pace, service-provider and enterprise customers are demanding greater reliability and availability. When every minute of downtime can mean millions of dollars in lost revenue and embarrassing headlines, companies are eagerly looking for solutions to make their systems highly available.
One technique for increasing reliability and availability is redundancy, where active and standby resources are provided along with techniques to switch to the standby resource when the active resource fails.
On such technique, developed by the assignee of the present application, is to backup the active interface, or port, on a switch with a standby interface. In the following this technique will be referred to as “flexlink”. Flexlink allows users to configure a first Layer 2 interface of a switch to backup another Layer 2 interface of the switch. For a given set of virtual local area networks (VLANs), at any given time only one flexlink interface is in forwarding state (referred to as “active” link in the following) while the other link does not allow the traffic to pass through (referred to as “standby” link). Flexlink is generally used at the edge between access and distribution switches/routers. These distribution switches/routers include both Layer 2 (or data link layer) interfaces which use Media Access Control (MAC) addresses and Layer 3 (network layer) interfaces which use network (IP) addresses and will be referred to in the following as LAYER 2/LAYER 3 network devices.
The idea behind flexlink is that if one of the uplink fails, the edge switch still remains connected to the core network through the other uplink. With the flexlink configuration, only one of the uplinks is forwarding data at any given time and hence data forwarding loops are avoided.